The present invention relates generally to a braking device for a hydraulic elevator and in particular to a backup apparatus for operating an elevator brake upon failure of the primary and secondary power supplies.
The U.S. Pat. No. 1,903,573 shows an emergency control by means of which an elevator car of a hydraulic elevator is guided, in case of an emergency, automatically to the next-following floor, whereupon the car doors for the evacuation of the elevator car are opened. In case of a power failure, a battery fed inverter generates the necessary supply voltage for an emergency control circuit.
It is a disadvantage of this known emergency control device, that the device will only function in case the hydraulic circuit functions correctly and sufficient pressure is present in the hydraulic system.